The present invention relates generally to an intraluminal radiation system for the delivery of treatment elements by way of a catheter to a selected location within the intraluminal passageways of a patient. More particularly, the present invention relates primarily to an improved transfer device for handling the treatment elements and delivering them to the catheter.
Since the late 1970""s balloon angioplasty techniques have become widely used for opening blockages in coronary arteries. Briefly, the enlargement of the artery is achieved by advancing a balloon catheter into a narrowed portion of the artery and inflating the balloon to expand the diameter of the artery, thus opening the artery for greater blood flow. Atherectomy techniques, in which blockages are removed or reduced in size, have also been used to the same end.
While balloon angioplasty has proved an effective way of opening the coronary arteries, in a significant number of cases the arteries narrow again at the location where the balloon was expanded, such narrowing being termed restenosis. Restenosis is believed to be caused by formation of scar tissue at the site of the angioplasty that results from the injury to the artery caused by the inflation of the balloon. More recently, intraluminal radiation has been used after angioplasty or atherectomy to treat the affected area of the artery to inhibit cell proliferation and wound healing response and, consequently, help to prevent restenosis. Methods and apparatus for such intraluminal radiation treatment are disclosed in U.S. Pat. Nos. 5,899,882 and 6,013,020, and applications Ser. No. 09/304,752, filed May 4, 1999, and Ser. No. 09/469,510, filed Dec. 22, 1999, all of which are incorporated herein by reference. These applications generally disclose an apparatus comprising a catheter, which is inserted intraluminally into the patient and advanced to the site of the area to be treated, and a transfer device for facilitating either the hydraulic or pneumatic advancement and retrieval of individual radioactive treating elements or xe2x80x9cseedsxe2x80x9d along the catheter to and from the treatment site. A plurality of treatment elements comprises a xe2x80x9csource train.xe2x80x9d
As with any device inserted into the vascular system, it must have sufficient integrity to insure that no pieces or elements are separated from or exit the device into the vascular system. This is particularly true for the treating elements which are moved to and from the distal end of the catheter. Additionally, because the device is intended to use radioactive treating elements, there is a heightened need for safety to prevent any unintended exposure of either the patient or the user to radioactivity.
Actual use of the apparatus described in the above-identified patents and co-pending applications has suggested several areas where the device could be improved to reduce the possibility of having treatment elements escape from the system, thus enhancing patient and user safety.
Consequently, it is the principal object of the present invention to provide a transfer device and catheter assembly that has additional safeguards to protect the patient and user for unintended exposure to radiation.
More particularly, it is an object of the present invention to provide a transfer device/catheter assembly in which the treatment elements cannot be inadvertently released from the transfer device.
Additionally, it is an object of the present invention to provide a transfer device capable of advancing and retrieving source trains of varying lengths for treatment of different sized lesions. More particularly, the transfer device is adapted to receive interchangeable cartridges which house source trains of varying lengths.
Another object of the present invention is to provide a delivery system that requires both automation and manual manipulation to successfully and safely advance the user through the treatment procedure. More particularly, the transfer device automatically creates the pressurized fluid flow, senses the presence or absence of the treating elements within the transfer device, and permits or prevents movement of the gate mechanism to the open or closed position through the use of electromechanical means and prompts the user to sequentially follow the appropriate manual steps for safely providing treatment to the patient.
These objects, as well as others which will become apparent upon reference to the following drawings and detailed description, are provided by a system comprising a microprocessor-controlled transfer device and a separate catheter for intraluminal treatment of a selected site in a body of a patient by at least one treating element advanced from a removable treating element cartridge received in the transfer device into a lumen of the separate catheter by means of pressurized fluid controlled by a fluid control switch moveable between send and return positions. A safety interlock is provided for preventing both (1) the disassembly of the system unless the treating element resides in the treating element cartridge and (2) the actuation of the fluid control switch unless the system is assembled. The safety interlock comprises a first lock moveable from a first position to a second position only if both the catheter and the treating element cartridge are secured to the transfer device. The first lock blocks the movement of the fluid control switch to the send position when in its first position and prevents disassembly of either the catheter or the treating element cartridge from the transfer device when in its second position. The fluid control switch further locks the first lock into its second position when the fluid control switch is in the send position.
In a preferred embodiment, the safety interlock comprises a spring having two arms, each arm being engaged by one of the catheter or the treating element cartridge when attached to the transfer device. A slidable switch is provided including a yoke that is moveable from a first position to a second position to capture the arms of the spring and to lock both the catheter and the treating element cartridge to the transfer device only if each arm of the spring is engaged by one of the catheter and treating element cartridge. Each arm of the spring is independently capable of blocking movement of the yoke from its first position to its second position if the spring arm is not engaged by one of the catheter or treating element cartridge.
The fluid control switch actuates a gate mechanism moveable between open and closed positions to respectively permit or prevent the treating element from moving out of the treating element cartridge when subjected to pressurized fluid. A solenoid is provided to lock the gate mechanism in the open position and disengages the gate mechanism to permit it to close only when the treating element resides in the treating element cartridge.
Photo interrupters or other sensors may be associated with the first lock or the fluid control switch to detect their position and generate a signal sent to the microprocessor to permit the treatment to continue in accordance with the position of the first lock and the fluid control switch.
In a further aspect of the invention, a system is provided for detecting whether the treating element resides at a targeted location along the lumen of the transfer device. The detection system comprises a pressure transducer that is in fluid communication with the lumen of the transfer device so as to be capable of measuring the fluid pressure difference across the targeted location of the lumen. Circuitry is provided for comparing the measured pressure difference to a reference pressure difference corresponding to the pressure difference at the targeted location when the treating elements are stored at the targeted location under fluid pressure. A signal generator provides a signal when the measured pressure difference differs from the reference pressure difference by more than a predetermined amount. The signal may activate an optical signal and/or a mechanical interlock, the latter preventing separation of the catheter from the transfer device and preventing closure of the gate when activated by a signal from the signal generator corresponding to the pressure difference encountered when the treating element does not reside at the targeted location.
In an alternate embodiment of this aspect of the present invention, the pressure transducer is in fluid communication with the lumen of the transfer device so as to be capable of gauging the fluid pressure at a single point along the lumen of the transfer device and distal to where the treatment elements reside at a targeted location along the lumen of the transfer device. The measured pressure at this single point is compared to either a predefined pressure or a reference pressure corresponding to the pressure at the same point when the treating elements are stored at the targeted location under fluid pressure. A signal generator provides a signal when the measured pressure differs from the predefined or reference pressure by more than a predetermined amount.